Method for making glass enamels sulfide resistant



Patented Apr. 7, 1953 W. Pel'z, Parma, hio,.assignor to FerroCorporation, a corporation of Ohio METEIOD Robert NoDrawin'g,Application May '21, 1 49,

- Serial No. 94,727

This invention relates as indicated to a new and novel methodforrendering glass enamels resistant to sulfide attack.

laims. 11(01. 41--=4 2 i Heretofore, lead bearing glass enamels fordecorating glass articles, such as tumblers, bottles, lampshades, etc.-,have had the undesirable property of turning brown upon standing. It hasbeen found that the hydrogen sulfide present in the atmosphere,particularly in industrialareas,

reacts with any free lead in the glass enamels to- My present inj form acoating of lead sulfide. vention relates to a process for treatingsuchenamels after application to prevent sulfide dis:

coloration. I It is therefore a principal object of my invention toprovide a method for preventing glass ar ticles decorated with leadbearing enamels from becoming discolored. I

A further object of this invention is to provide an economical method ofpreventingsulfide dis coloration which is applicable to any lead bearingglass enamel.

To the accomplishment of the foregoing ends, said invention, then,comprises the features hereinafter fully described and particularlypointed out in the claims, setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of but afew of the various ways in which the principle of'the invention may beemployed.

Broadly stated, this invention provides a method for rendering glassarticles, decorated with lead bearing enamels, sulfide resistant which vfree lead ions. The ground enamel when applied to at; glass articleis,firedand during this firing process the free lead ions cometo thesurf-aceof the decorated article. It is these free lead ions that thenreact with the hydrogen sulfideat the 7 atmosphere to form brown leadsulfide on the sura bath of a dilute acid, such as, acetic, nitric, or

hydrochloric the free lead ions are dissolved and 7 then with a thoroughwater rinsing arewashed 2' away thus leaving the surface free of leadand thus preventing theformation of lead sulfide.

Although the foregoing theory is assumed to be correct I do not want tobe'bound'by it. The fact remains that when the process of the presentin? 1' vention is used the treated articles are sulfide re '"sistant anddo not become sulfide stained upon exposure to hydrogen sulfide.

" -I-have tried-various salts such as ammonium nitrate, ammoniumacetateand calcium acetate in place of the aforementioned acids.Although .they reduced-sulfide attack considerably they do notgiveascomplete resistance as the acids. Inthe preferred embodiment of myinvention I use from a /4% to 5% solution of acetate acidor hydrochloricacid, immerse the decorated article in the acid'bath for about 15minutes and then rinse the acid treatedarticle in water containing soapor some other detergent. Or, in'general apH of from about 1.0 to about4.0 has been found to j be the desired range for carrying out theprocess of my invention. The length of time the decorated article isleft in the acid bath is inversely proportional to the concentration ofthe acid or in terms of pH thelength of time the decorated article isleft in the acid bath is directly pro:

portional to the pH. That is, the stronger the f acid solution theshorter the time the" decorated I article is left inthe acid bath. It isimperative that adequate rinsing is done so that all of the dissolvedlead is removed from the surface.

, This process is applicable to any lead bearing glass enamel of whichthe following are given as examples of such enamels. V r

72. 5 lbs. P50 67. 5 lbs. PbO 5.0 lbsLP20a 5. O lbs. B 0: 22. 5 lbs.SiOz 27. 5 lbs. SiQz O. 5 lb. A1203 0. 51b. A1203 0. 551D. T102 1.0 lb.T101 .-0 lb. Li2O -1. 0 lb. LizO so that the effectiveness of thesulfide resist ance could be determined the following test was devisedandused:

H2S was bubbled through distilled water at room temperature (-75 F.) for10 minutes. The bubbling of the H28 was thenadjusted so thatapproximately bubbles rose per minute.

] Panels with the glass enamel were placed in this solution at such anangle as to allow the Has to, risei-n contact with-the glass enamel. Thepanels" were immersed in the H28" bathfor 5 minutes,

after which they were removed and allowed to air dry. No wiping ofsamples was done.

As illustrative of the several ways in which the process of my inventionmay be carried out, reference may be had to the following examples:

ANo treatmentstandard.

B-Dipped in 4% acetic bath for 1 minute and rinsed in water spray.

C-Dlpped in 4% acetic bath for 1 minute, washed in water containingdetergent and rinsed in a water spray.

All samples were then subjected to the previously discusssed HzS test.

Reflectometer readings were then again taken on the treated samples. Thefollowing reflectometer readings were noted.

The results of the aforegoing test were as follows:

(1) The untreated sample showed severe sulflde staining whereas thetreated samples remained white and unstained.

(2) The treated samples showed increased reflectance.

(3) It is to be noted again there is no reflectometer reading for thestandard sample after exposure to HzS. This is because the sample was sobadly sulfide stained a reading could not be taken.

It is to be noted that care in the preparation of the HCl solution mustbe exercised. I have found that when a decorated article isinadvertently left in the HCl bath too long or if the acid concentrationis too strong the HCl will etch the surface of the glass enamel. Forthis reason I prefer the use of the acetic acid bathvsince the aceticacid is a weaker acid than the HCl and the concentrations more easilycontrolled.

From the foregoing discussion and examples it can readily be seen thatby using my process a glass article decorated with a lead bearing glass5 enamel can withstand the most severe sulfide conditions and also beincreased in reflectance.

Blue Green Amber Before After Before After Before After Treat- Treat-213g Treat- Treat- 1$? Treat- Treat- D fiermeut ment ment ment ment mentence Example II 4'! x 4" were prepared as in Example I and reflectometerreadings taken. The panels were then divided into groups and treated inthe following manner:

ANo treatment-standard.

B-Dipped in 4% HCl bath for 1 minute and rinsed in water spray.

(l-Dipped in A% HCl bath for 1 minute, washed in water containingdetergent, and rinsed in a water spray.

All samples were then subjected to previously mentioned HzS test.

Reflectometer readings were then again taken on the treated samples. Thefollowing reflectometer readings were noted.

The use of the expression lead bearing glass enamel is not to beconfused with the expression lead bearing glass. Those versed in the artwill readily recognize the differences which exist between a glass andan enamel. Also it is readily appreciated (by those versed in the art)that in the manufacture of a glass enamel the enamel forming materialsare reduced to molten condition, fritted into water, and very finelyground before applied to a work piece, whereas,

in the manufacture of a lead glass the glass forming materials arereduced to a molten condition and in such condition molded into thedesired objects without any of the intermediate steps as performed inthe glass enamel.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims or the equivalent of suchbe employed.

I therefore particularly point out and distinctly claim as my invention:

1. The method of rendering resistant to sulfide staining the surface ofa glass article decorated with a lead bearing colored glass enamel thecomposition of which, calculated on the basis of the oxides, is morethan 50% lead, which comprises subjecting such decorated surface to abath of a dilute solution of an acid havin a pH of from about 1 to about4 for a period of from about 1 to Blue Green Amber Before After BeforeAfter Before After Treat- Treat- 2 5: Treat- Treat- 2 5 Treat- Treat-2g?" ment ment ment ment Ce ment ment A. 60. 5 0. 0 0. 0 58. 4 O. 0 O. O56. 6 0. 0 0. U B--. 60. 4 66. 2 +5. 8 58. 0 61. 4 +4. 2 55. 5 59. 9 +4.4 C- 61. 0 66. 3 +5. 9 58. 2 62. 7 +4. 5 56. 6 60. 6 +4. 2

about 5 minutes, the length of which period is inversely proportional tothe pH of the acid solution and not sufficient to decrease thereflectance of said surface and then thoroughly water washing the thustreated surface.

2. The method of rendering resistant to sulfide staining the surface ofa glass article decorated with a lead bearing colored glass enamel thecomposition of which, calculated on the basis of the oxides, is morethan 50% lead, which comprises subjecting such decorated surface to abath comprising from about 4% to about 5% of an aqueous acid solutionfor about 1 to about 5 minutes, said time for the acid treatment beinginversely proportional to the acid concentration and not suificient todecrease the reflectance of said surface and then thoroughly waterwashing the thus treated surface.

3. The process as in claim 2 said acid bein acetic acid.

6 1 4. The process as in claim 2 said acid being ydrochlorio acid.

5. The process as in claim 2 said acid bei nitric acid.

ROBERT W. PELZ.

REFERENCES CITED The following references are of record in the flle ofthis patent:

UNITED STATES PATENTS

1. THE METHOD OF RENDERING RESISTANT TO SULFIDE STAINING THE SURFACE OFA GLASS ARTICLE DECORATED WITH A LEAD BEARING COLORED GLASS ENAMEL THECOMPOSITION OF WHICH, CALCULATED ON THE BASIS OF THE OXIDES, IS MORETHAN 50% LEAD, WHICH COMPRISES SUBJECTING SUCH DECORATED SURFACE TO ABATH OF A DILUTE SOLUTION OF AN ACID HAVING A PH OF FROM ABOUT 1 TOABOUT 4 FOR A PERIOD OF FROM ABOUT 1 TO ABOUT 5 MINUTES, THE LENGTH OFWHICH PERIOD IS INVERSELY PROPORTIONAL TO THE PH OF THE ACID SOLUTIONAND NOT SUFFICIENT TO DECREASE THE REFLECTANCE OF SAID SURFACE AND THENTHOROUGHLY WATER WASHING THE THUS TREATED SURFACE.